Spark plug shield



Aug. 16, 1955 E. LUCAS 2,715,654

SPARK PLUG SHIELD Filed May 16, 1952 WINVENTOR.

BY LyleEiLlwas H 4 fl ATTORNEYS United States Patent SPARK PLUG SHIELD Lyle E. Lucas, North Canton, Ohio Application May 16, 1952, Serial No. 288,195 2 Claims. (Cl. 174--77) The invention relates to shields for spark plugs, and more particularly to a flexible rubber shield for preventing short-circuiting of the spark plug by moisture condensing on the surface thereof.

A principal object of the invention is to provide such a shield having means thereon for absorbing any moisture which may condense upon the spark plug when it is inactive and from which the moisture is expelled when the spark plug becomes heated in operation.

Another object is to provide a shield of this character which may be easily and readily applied to an existing spark plug, or which may be incorporated as original equipment on a new spark plug.

A further object is to provide a rubber shield of this character having a molded ring of suitable absorbent material, such as alumina, enclosed therein and surrounding the spark plug.

A still further object is to provide a shield of the type referred to having reduced vertical and angular necks for the attachment of either straight or angular connectors to the spark plug, each neck being originally closed by a thin diaphragm, either one of which may be torn out to insert the connector.

Another object of the invention is to provide such a spark plug shield designed to fit upon a standard size 14 mm. spark plug, and having a removable adapter arranged to be inserted into the lower end thereof for fitting upon a small size 10 mm. spark plug.

A further object is to provide such an adapter with a thin diaphragm whereby the shield with the absorbent ring therein may be shipped and stored with the adapter inserted in its lower end, to seal the absorbent ring against moisture.

The above objects together with others which will be apparent from the drawing and following description,

or which may be later referred to, may be attained by constructing the improved spark plug shield in the manner hereinafter described in detail and illustrated in the accompanying drawing, in which:

Fig. 1 is a vertical or longitudinal, sectional view of a rubber spark plug shield embodying the invention;

Fig. 2 a similar view showing the absorbent ring within the shield;

Fig. 3 a vertical, sectional view of the shield with absorbent ring therein applied to a standard size spark plug, with angular connection;

Fig. 4 a top plan view of the shield;

Fig. 5 a view similar to Fig. 3, showing the shield with adapter therein, applied to a small size spark plug, with straight connection;

Fig. 6 a detached, sectional view of the adapter; and

Fig. 7 a fragmentary, sectional view showing a modified form of angular neck.

Referring first to Fig. 3, a conventional standard size 14 mm. spark plug is shown, including the usual metal body 10 with hexagonal portion 11 at its upper end and reduced threaded lower end 12. The usual porcelain insulator is indicated at 13 and the binding post 14 is 2,715,654 Patented Aug. 16, 1955 located at the upper end of the spark plug for connection of the usual metal connector 15, which in this case is shown as an angular connector, for attaching the conductor wire 16 for supplying current to the terminals 17 beneath the threaded section 12 of the spark plug.

The improved shield to which the invention relates is indicated generally at 18 and is formed of flexible rubber, preferably of substantially cylindrical shape, having the enlarged, intermediate portion 19 terminating in the inwardly disposed annular bead 20, below which is formed the reduced portion 21 terminating in a similar inwardly disposed annular bead 22.

The upper end of the shield may be conical, as at 23, terminating in the reduced neck 24, preferably having the annular rim 25 and provided with a thin diaphragm 26. At one side of the shield 18, above the enlarged portion 19, is provided an angular neck 27 with enlarged rim 28 at its end and provided with a thin diaphragm 29, which may be located at the inner end of the neck, as shown in Fig. l, or as indicated at 29a in Fig. 7, may be formed at the outer end of the neck 27.

Within the enlarged, annular pocket 19 of the shield is located the dehydrator ring 30 which is preferably a molded ring of suitable absorbent material such as alumina. The ring may be molded with a binder and then fired, the firing burning out the binder and leaving the alumina in an activated condition. The advantage of using alumina as a hydrator is that it is long lasting and easily reactivated by the application of heat.

An adapter, indicated generally at 31, and shown detached in Fig. 6, is provided for insertion into the lower end of the shield for adapting the same to a small size spark plug.

This adapter is also made of flexible rubber and has the central annular rib 32, adapted to be received between the beads 20 and 22 in the lower end of the shield, and the upper and lower reduced portions 33 and 34 adapted to fit within the annular beads 20 and 22 of the shield. A thin diaphragm 35 is formed at the upper end of the adapter.

Referring to Fig. 5, a small size or 10 mm. spark plug is shown, comprising the metal body 10a with hexagonal portion 11a, a reduced threaded lower end 12a, porcelain insulator 13a and binding post 14a at its upper end for receiving the usual metal connector, which in this case is shown as a straight connector 15a, attached to the conductor wire 16a for supplying current to the terminals 17a.

In applying the shield to a spark plug, assuming that an angular connector is to be used, as shown in Fig. 3, the diaphragm 29 is torn out of the neck 27 so that the connector 15 may be inserted therethrough.

A slit or self sealing incision is made in the diaphragm 26 of the other neck, as indicated at 36 in Fig. 3, as by puncturing with a sharp knife blade. Such an incision may be made in each of the diaphragms 26 and 29, at the factory, so that when either diaphragm is torn away, to permit the insertion of a connector, the self sealing incision will remain in the other diaphragm.

The hexagonal portion 11 of the metal body of the spark plug is received between the internal, annular beads 20 and 22 in the lower end of the shield, as shown in Fig. 3. The molded ring 30 is thus located around and spaced from the porcelain insulator 13 of the spark plug.

As the reduced lower portion 21 of the shield fits tightly around the metal body of the spark plug and the neck 27 fits tightly upon the connector 15 and conductor 16, forming a seal at these points, moisture is excluded from the spark plug.

When the spark plug is installed but inactive, any moisture which might condense on the surface thereof is absorbed by the dehydrator ring 30. Any moisture which might remain on the plug will be vaporized by the heat generated in the use of the plug and then absorbed by the ring 30.

Prolonged and uninterrupted use of the spark plug may drive the moisture from the dehydrator through the slit 36 in the diaphragm 26. However, since alumina absorbs a relatively large quantity of moisture, it may be easily reactivated by applying heat thereto on removal from the spark plug.

As shown in Fig. 5, with the adapter 31 inserted into the lower end of the shield, the adapter will fit over the hexagonal portion 11a and upon the metal body a of the spark plug forming a seal at this point. It is understood of course that the diaphragm 35 should be torn from the adapter when the same is to be used upon the small size spark plug as shown in Fig. 5.

The diaphragm may be torn from the upper neck 24 to permit the use of the straight connector a in which case a slit 36 may be formed in the diaphragm 29 of the neck 27.

In order to protect the alumina ring 30 and seal the same against moisture during shipping and storage of the shield, the adapter 31 may be inserted into the lower end of the shield, as shown in Fig. 2, thus completely enclosing and sealing the ring.

In the foregoing description, certain terms have been used for brevity, clearness and understanding, but no unnecessary limitations are to be implied therefrom beyond the requirements of the prior art, because such words are used for descriptive purposes herein and are intended to be broadly construed.

Moreover, the embodiments of the improved construction illustrated and described herein are by way of example, and the scope of the present invention is not limited to the exact details of construction.

Having now described the invention or discovery, the construction, the operation, and use of preferred embodiments thereof, and the advantageous new and useful results obtained thereby; the new and useful constructions, and reasonable mechanical equivalents thereof obvious to those skilled in the art, are set forth in the appended claims.

I claim:

1. A shield for spark plugs comprising a hollow cylindrical flexible rubber shell of a size to surround a spark plug in spaced relation thereto, a spaced pair of internal annular beads at the lower end of said shell adapted to fit over the hexagonal metal portion of the spark plug, an enlarged cylindrical intermediate portion of the shell adapted to surround the insulation portion of the spark plug in spaced relation thereto, and a molded hollow cylinder of absorbent material located in said enlarged cylindrical portion of the shell surrounding and in spaced relation to the insulation portion of the spark plug, a vertical neck and an angular neck on the upper portion of the shell, and a thin integral drum type diaphragm closing one of said necks, said diaphragm having a self sealing incision therein to equalize internal and external air pressure upon the shell when a connector is located through the other neck.

2. A shield for spark plugs comprising a hollow cylindrical flexible rubber shell of a size to surround a spark plug in spaced relation thereto, a spaced pair of internal annular beads at the lower end of said shell adapted to fit over the hexagonal metal portion of the spark plug, an enlarged cylindrical intermediate portion of the shell adapted to surround the insulation portion of the spark plug in spaced relation thereto, and a molded hollow cylinder of moisture absorbent material located in said enlarged cylindrical portion of the shell surrounding and in spaced relation to the insulation portion of the spark plug, a vertical neck and an angular neck on the upper portion of the shell, and thin integral drum type diaphragms closing said necks and adapted to be selectively removed to receive a vertical or an angular connection respectively, each of said diaphragms having a self sealing incision therein to equalize internal and external air pressure upon the shell when a connector is located through the other neck.

References Cited in the file of this patent UNITED STATES PATENTS 1,898,064 Ridge Feb. 21, 1933 2,323,399 Jacobi July 6, 1943 2,352,158 Bishop June 27, 1944 2,428,608 Bass Oct. 7, 1947 2,617,848 Malone Nov. 11, 1952 FOREIGN PATENTS 290,820 Great Britain May 24, 1928 

